The long term goal of this project is to define the role and functions of basophilic leukocytes in human diseases having an immunologic basis. In addition, a more comprehensive analysis of the pathogenesis of cellular and humoral immunity in man will be undertaken. This analysis, based upon biopsies taken from normal human volunteers, will include histopathologic review of 1 micron Epon-embedded sections, fluorescent antibody study, and electron microscopic evaluation of a variety of lesions such as delayed hypersensitivity reactions to protein antigens and topically applied sensitizing agents (allergic-contact- dermatitis-lesions). The information obtained from normal volunteers on whom delayed cutaneous lesions have been elicited will provide the first comprehensive morphologic description of such lesions in man and will serve as a background for the interpretation of similar reactions occurring in a variety of tissues in patients with naturally occurring disease states having an immunologic basis. Our major effort during the current year has been to complete acquisition and carry out morphologic analysis of delayed hypersensitivity skin reactions in normal volunteers. In addition, selected biopsy material has been acquired from certain specific disease states of immunologic interest.